Integrated circuits, circuit assemblies and corresponding methods for their operation are known from the field of signal processing in general. In particular, such circuit arrangements can be used at an analog stage for amplifying a signal provided by a microphone or similar transducer.
In many applications, processing of signals having a high dynamic range is desirable. For example, when recording an audio or audio-visual performance using a portable device, both quiet and loud passages of the performance should be recorded with high-fidelity. However, in particular when using battery operated, mobile devices, the dynamic range of a processing device is often limited. For example, the dynamic range of an analog-to-digital converter used to convert an analog audio signal for a subsequent digital signal processing device may be restricted by the supply voltage available from the battery. In order to maintain a reasonable resolution over the entire signal range, some form of signal preconditioning may be used. For example, an analog signal provided by a microphone may be preamplified using an amplifier having an automatic gain control circuit. In this way, quieter passages of the performance can be amplified using a higher amplification setting, resulting in a greater signal amplitude, while louder parts of the performance can be amplified using a lower amplification setting.
In this context, US 2014/0185832 A1 discloses an assembly including the signal processing unit SPU shown in FIG. 4. A signal path SL guides from an analog signal input INA to an analog signal output OUTA. Within the signal path SL, an amplifier LNA is arranged to amplify the useful analog signal fed to the analog signal input INA and guides the amplified signal to the analog signal output OUTA. Coupled to the signal path SL and the amplifier LNA is an automatic gain control AGC controlling the gain of the amplifier LNA. Gain information about the current gain is provided by the automatic gain control AGC as a digital or analog signal which is delivered to a gain information output DGI. Thus, the signal processing unit SPU comprises an analog signal output OUTA and further the gain information output DGI.
The information provided at the gain information output DGI may be useful for further processing the amplified analog signal where information about the sensitivity of the signal processing unit SPU is needed. However, the circuit assembly disclosed in US 2014/0185832 A1 requires the provision of an additional terminal for providing the gain information. In particular in highly integrated circuits and miniaturized circuit design, the provision of an additional terminal may be problematic. Furthermore, such a circuit assembly may not be used in existing chip packages or circuit arrangements, which do not allow the provision of an additional terminal to supply the required gain information.